The present invention relates to a liquid filter according to the preamble of Patent Claim 1.
Known liquid filters often include barrier membranes and non-return valves to prevent liquid from flowing back out of the filter when the internal combustion engine is stopped. Such devices also prevent the liquid from flowing out of the filter when the filter is replaced.
Published German Patent application no. DE 41 40 140 describes a screw-on filter for liquids, in particular a lubricating oil filter for an internal combustion engine. Such a filter has a peripheral barrier membrane in the area of the liquid inlet which achieves the sealing function via a peripheral lip which fits sealingly against a cover plate of the replaceable filter. In addition, a non-return valve consisting of a cage, a spring arranged in the cage, and a valve body acted upon by the spring with spring force is mounted centrally in the interior of the filter medium, with a sealing fit being established between the valve body and the cage.
However, it is a disadvantage of this arrangement that many different parts are needed for the functioning of the non-return valve and the barrier membrane, and these parts are manufactured from different materials.